Recently, portable telephones have supported a TV telephone function in which it is possible to have a conversation using not only audio but also video. Also, on the other hand, in accordance with digitalization of TV broadcasting, a TV receiving function has been supported so that it is possible to watch TV also on portable telephones. In order to realize these functions, it is necessary for portable telephones to be provided with decoders for decoding stream data such as video and audio corresponding to each of the services in real-time. Also, in order to provide a plurality of services at the same time, it is necessary to include a plurality of decoders.
On the other hand, with the development of device technology, a decoder has been developed that corresponds to a plurality of stream data codecs. By including this decoder, it is possible to manufacture generic purpose portable telephones that do not specialize in their corresponding services, and thus there is an industrial advantage.
Hereinafter, an example of a portable telephone will be explained in which a plurality of decoders are included so that it is possible to correspond to a plurality of services. FIG. 17 is a diagram showing an outlined configuration of a portable telephone system and a display example of a portable telephone screen. FIG. 18 is a diagram showing an example of a hardware configuration of a portable telephone 1700.
Referring to FIG. 17, the portable telephone 1700 receives, with a communication antenna 1721, TV telephone data sent from another portable telephone (not shown) via a communication network 1701 and a telephone base station 1702. Then, the portable telephone 1700 decodes the received TV telephone data and displays the data on an LCD panel 1751 as a TV telephone application. Herein, an image display frame for the TV telephone application is taken as a TV telephone frame 1720.
Furthermore, the portable telephone 1700 receives, with a broadcast antenna 1711, TV broadcast data sent from a broadcast station 1703. Then, the portable telephone 1700 decodes the received TV broadcast data and displays the data on the LCD panel 1751 as a TV receiving application. Herein, a frame for displaying the TV receiving application is taken as a TV broadcast frame 1710.
Also, the portable telephone 1700 is provided with a speaker 1761 through which audio is output and keys 1731 with which the user controls operations of the TV telephone application and the TV receiving application described above. In the portable telephone 1700, description of other functions that do not directly relate to the present invention has been omitted.
Referring to FIG. 18, the portable telephone 1700 is provided with at least a CPU 1801 for controlling the entire device, a ROM 1802 and a RAM 1803 for storing a program and the like, a bus 1805, a TV receiving portion 1810 for receiving TV broadcast data obtained via the broadcast antenna 1711, a communication portion 1820 for sending and receiving TV telephone data via the communication antenna 1721, a key controller 1830 for controlling the on/off of the keys 1731, two decoders A 1841 and B 1842 for decoding AV streams received by the TV receiving portion 1810 and the communication portion 1820, an LCD controller 1850 for letting the decoded result be displayed in the image display frames 1710 and 1720 on the LCD panel 1751, and a D/A converter 1860 with which audio data decoded by the decoder A 1841 and the decoder B 1842 is converted into an analog signal and output to the speaker 1761.
Next, the relationship between decoders and application image display frames in conventional techniques will be explained.
FIG. 19 shows the relationship between decoders and application image display frames in a general conventional technique. In a screen display example, the TV receiving portion 1810 is connected to the decoder A 1841, and the communication portion 1820 is connected to the decoder B 1842, respectively, in a fixed manner. Data decoded by the decoder A 1841 is displayed on the LCD panel 1751 as the image display frame 1710 for a TV broadcast application, and data decoded by the decoder B 1842 is displayed on the LCD panel 1751 as the image display frame 1720 for a TV telephone application. Each of the applications is output through not only the image display frames but also the speaker 1761 as audio. An output portion 1880 in FIG. 18 includes both the LCD panel 1751 and the speaker 1761.
Furthermore, there is a technique in which as a method for connecting decoders, in an AV system that includes a display apparatus connected with a plurality of AV devices and having a decoding function, a decoder that is suitable (can perform a process) is selected in accordance with a signal to be processed, and the signal is decoded. In this technique, as shown in FIG. 20, for example, in the case where a plurality of kinds of stream data are input at an IEEE 1394 interface 2001, the stream data is distributed to optimal decoders by a data dividing switch 2002.
Generally, when a plurality of decoders are included in a portable telephone, it is preferable that high-performance decoders are included. However, there is the trade-off relationship between the performance, and the electric power consumption and manufacturing cost of a decoder. Therefore, a large number of manufacturers are confronted with a choice below from the viewpoint of the balance between services provided by portable telephones and their price.
The choice is whether only high-performance decoders are included so that the service quality is given priority over the portable telephone price, or only low-performance decoders are included so that the portable telephone price is given priority over the service quality. Other than this, a choice is conceivable in which a plurality of decoders having a difference in their performance are included so that the intermediate level is taken for the portable telephone price and the service quality. More specifically, a high-performance decoder is allocated to the main services and a low-performance decoder is allocated to the other services.
For example, it is assumed that the decoder A 1841 is a high-performance decoder in which the electric power consumption is high but the image quality is good, and that the decoder B 1842 is a low-performance decoder in which the electric power consumption is low but the image quality is poor. It is also assumed that both of the decoder A 1841 and the decoder B 1842 correspond to both of a codec for TV telephone data and a codec for TV broadcast data.
Herein, there is the problem that in the conventional configuration of a portable telephone, a combination of a decoder and input data thereinto is allocated in a fixed manner at least at the time of starting a service, and thus the decoder cannot be switched dynamically during the service. For example, the case will be described in which while watching TV with high-quality images using the high-performance decoder A 1841, there is an incoming TV telephone call. In this case, although the interest of the user has shifted to the incoming TV telephone, the high-performance decoder A 1841 has been already allocated for watching TV, and thus the TV telephone has to use the low-performance decoder B 1842 and is performed at a low quality.